Cast cylindrical brushes, also known as cleaning brushes, are cleaning brushes usually made of polyvinyl alcohol (PVA) and conventionally used in automatic cleaning systems to provide a post CMP (Chemical Mechanical Planarization) process to effectively clean surfaces of substrates such as semiconductor wafers or other disc-shaped substrates. Cleaning brushes are also used in cleaning systems to clean and dry glass and other non-disc-shaped substrates in flat panel display manufacture, glass production, and printed circuit board assembly. Cleaning brushes preferably have a length as short as 50 millimeters or as long as 10 meters, for example.
The cleaning brushes are located on and driven by a central brush core in the cleaning process. An accurate and stable connection between the cleaning brush and the central brush core is desirable. The cleaning brushes may have nodules on their outer surface to help clean the substrate.
The cleaning brushes are expected to accurately rotate on their axis and provide a generally cylindrical surface with a generally consistent nodule pressure pattern over their useful life, which defines optimum cleaning of the entire substrate surface in the least amount of time with minimal damage to the substrate surface. In some cases, the cleaning brush is formed around the central brush core. For example, the brush core may be placed in a mold and a mixture of chemicals comprising one or more polymer precursors, such as vinyl alcohol, is injected into the mold to form the cleaning brush around the central brush core.
Traditional cleaning brushes feature nodules, typically cylindrical, that protrude perpendicularly from the body of the brush (FIGS. 1A-1B). Under typical operating conditions necessary for proper cleaning of the semiconductor surface after CMP, traditional brush nodules generate excessive shear force since they protrude perpendicularly from the body of the brush. As a result, the excessive shear force, along with an excessive normal force, adversely affects the exposed surfaces to be cleaned by generating mechanically induced defects, like scratches. Scratches generated by the cleaning brush adversely affect the performance, yield, and reliability of the semiconductor device.
As a result, it would be desirable to have a cleaning brush in which fewer particles may get trapped between the cleaning brush and the substrate. Additionally, it would also be desirable to have a cleaning brush in which the shear force and the normal force applied onto the substrate from the cleaning brush is reduced, resulting in less mechanically induced defects generated by the cleaning brush.